Solid electrolytic capacitors (e.g., tantalum capacitors) have been a major contributor to the miniaturization of electronic circuits and have made possible the application of such circuits in extreme environments. Conventional solid electrolytic capacitors may be formed by pressing a metal powder (e.g., tantalum) around a metal lead wire, sintering the pressed part, anodizing the sintered anode, and thereafter applying a solid electrolyte. Unfortunately, however, it has traditionally been difficult to form the dielectric layers of such capacitors at the high voltages often required in high voltage power distribution systems. For example, most formation processes require that a current is applied to the anodizing solution in a decreasing, stepwise fashion for a relatively long period of time (e.g., over 600 minutes) to achieve the desired voltage level. The present inventors have found, however, that overheating often occurs during such a process, which can lead to cracking in the dielectric and also result in a dramatic increase in the leakage current exhibited by the capacitor.
As such, a need currently exists for a solid electrolytic capacitor having improved performance in very high voltage environments.